Equivalent fractions and multiplying by a whole number

Two fractions with different numbers can have the same value, such as 2/5 and 4/10. To find a missing number, look at how the known numbers changed. In 2/5 = ?/10, the denominator went from 5 to 10, so it was multiplied by 2. We must multiply the numerator by 2 too: 2 × 2 = 4. So 2/5 = 4/10. In 3/4 = 9/?, the numerator went from 3 to 9, which is × 3, so the denominator is 4 × 3 = 12. We can also go the other way by dividing: 9/12 = 3/4 because 9 ÷ 3 = 3 and 12 ÷ 3 = 4. The rule is always the same: whatever you do to the top, you do to the bottom. Check with a bar or by dividing back.